Camera system, camera body, and control method of camera system

ABSTRACT

According to one embodiment, camera system includes interchangeable lens and camera body. Camera body includes image sensor; reception circuit configured to acquire, first lens information including distortion correction information for correcting distortion of image pickup optical system, and function indicating correlation between shape of distortion on image plane, which corresponds to driving amount of vibration reduction optical system, and shape of distortion on image plane, which corresponds to displacement amount between optical axis and image center of photographed image; and processer configured to calculate converted displacement amount by using function, and to execute distortion correction, based on distortion correction information and converted displacement amount.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2016-084739, filed Apr. 20,2016, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to a camera system, a camera body, and acontrol method of the camera system.

BACKGROUND

As a method for suppressing blur (image blur) in a photographed imagedue to a camera shake or the like in an image pickup apparatus, there isknown an optical-type blur suppressing process which drives a vibrationreduction optical system in accordance with blur that occurred, thevibration reduction optical system being provided to constitute a partof an image pickup optical system. In addition, a photographed image,which is obtained via the image pickup optical system, distorts due toan influence of distortion or the like of the image pickup opticalsystem. Such distortion or the like is, in usual cases, corrected by ageometrical conversion process. In an image pickup apparatus which isproposed in Jpn. Pat. Appln. KOKAI Publication No. 2015-015587 (patentdocument 1), a component (dynamic component), which varies due todecentering of the image pickup optical system by the driving of thevibration reduction optical system, and a component (static component),which does not vary, are divided, and the distortions of the respectivecomponents are individually corrected, thereby to improve the precisionof distortion correction.

However, in the method of patent document 1, since two distortioncorrections are executed, the processing load increases. In addition,since parameters for correction, which are used in the respectivedistortion corrections, are needed, a necessary memory resourceincreases.

SUMMARY

According to one embodiment, a camera system includes an interchangeablelens and a camera body on which the interchangeable lens is mounted. Theinterchangeable lens includes an image pickup optical system includingat least a vibration reduction optical system which is driven in adirection perpendicular to an optical axis, the image pickup opticalsystem being configured to form an image on an image plane; a bluramount detection sensor configured to acquire a blur amount of thecamera system; and a blur correction actuator configured to drive thevibration reduction optical system by a driving amount corresponding tothe blur amount. The camera body includes an image sensor configured tophotograph the image formed by the image pickup optical system, and toacquire a photographed image; a reception circuit configured to acquirefirst lens information including distortion correction information forcorrecting distortion of the image pickup optical system, and a functionindicating a correlation between a shape of distortion on the imageplane, which corresponds to a driving amount of the vibration reductionoptical system, and a shape of distortion on the image plane, whichcorresponds to a displacement amount between the optical axis and animage center of the photographed image; and a processer configured toconvert the displacement amount between the optical axis and the imagecenter of the photographed image by using the function, therebycalculating a converted displacement amount, and to execute distortioncorrection on the photographed image, based on the distortion correctioninformation and the converted displacement amount.

According to the present invention, there can be provided a camerasystem and a camera body, which can execute, by a simple method,distortion correction with high precision, taking into account a shapevariation of distortion on an image plane due to decentering of avibration reduction optical system.

Advantages of the invention will be set forth in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the invention. The advantages of the inventionmay be realized and obtained by means of the instrumentalities andcombinations particularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1A is a view for explaining image blur.

FIG. 1B is a view for explaining image blur.

FIG. 2A is a view for explaining an optical system shift-type blursuppression process.

FIG. 2B is a view for explaining an imaging element shift-type blursuppression process.

FIG. 2C is a view for explaining an electronic-type blur suppressionprocess.

FIG. 3A is a view illustrating a photographed image in which no imageblur occurs.

FIG. 3B is a view illustrating a photographed image in which image bluroccurs.

FIG. 3C is a view illustrating a photographed image after the imagingelement shift-type blur suppression process or electronic-type blursuppression process was applied to the image blur of FIG. 3B.

FIG. 4 is a view illustrating a photographed image after the opticalsystem shift-type blur suppression process was applied to the image blurof FIG. 3B.

FIG. 5 is a view illustrating an example of a relationship between ashape variation of distortion due to decentering of a vibrationreduction optical system and a shape variation of distortion due to adisplacement between an image center and an optical axis of an imagepickup optical system.

FIG. 6A is a view illustrating an example of a correlation between adriving amount of a vibration reduction optical system and a drivingamount of an imaging element, which are similar in shape of distortionon an image plane.

FIG. 6B is a view illustrating an example of a correlation between adriving amount of a vibration reduction optical system and a drivingamount of an imaging element, which are similar in shape of distortionon an image plane.

FIG. 7 is a view illustrating an external appearance of aninterchangeable lens and a camera body of an image pickup systemaccording to a first embodiment.

FIG. 8 is a view illustrating a configuration example of a controlsystem of the image pickup system in the first embodiment.

FIG. 9 is a block diagram illustrating, as blocks, functions which asystem controller includes.

FIG. 10 is an explanatory view illustrating an example of aconfiguration for driving a vibration reduction optical system of anoptical system driving unit.

FIG. 11 is a block diagram illustrating, as blocks, functions which anLCU includes.

FIG. 12 is an explanatory view for explaining an operation of acorrection amount calculator.

FIG. 13 is a flowchart illustrating an example of an operation relatingto distortion correction of a camera body and an interchangeable lens.

FIG. 14 is an explanatory view illustrating an example of a referenceposition conversion function.

FIG. 15 is a view illustrating a configuration of an image pickup systemaccording to a second embodiment.

FIG. 16 is a block diagram illustrating, as blocks, functions which ablur correction microcomputer includes.

FIG. 17 is an explanatory view for explaining an operation of acorrection amount calculator.

FIG. 18 is an explanatory view for explaining an operation of acorrection amount calculator.

FIG. 19 is an explanatory view for explaining an example of aconfiguration of an imaging element actuator for actuating an imagingelement.

FIG. 20 is a block diagram illustrating, as blocks, functions which asystem controller according to the second embodiment includes.

FIG. 21 is an explanatory view for explaining an operation of acorrection amount calculator in an LCU according to the secondembodiment.

FIG. 22 is a flowchart illustrating an example of an operation relatingto distortion correction of a camera body and an interchangeable lensaccording to the second embodiment.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings. To begin with, the principle ofdistortion correction according to each of the embodiments of theinvention is explained. Thus, an image blur suppression process(vibration reduction process) is explained. FIG. 1A and FIG. 1B areviews for describing image blur. FIG. 1A is a view illustrating arelationship between a subject and an image pickup apparatus at a timewhen no image blur occurs. FIG. 1B is a view illustrating a relationshipbetween the subject and image pickup apparatus at a time when angularblur of angle θ occurs at an image center of the image pickup apparatus.A z-axis in FIG. 1A and FIG. 1B is, for example, a direction which isparallel to the ground surface, and a y-axis is, for example, adirection which is perpendicular to the ground surface.

A light flux from an arbitrary object point of a subject forms an imageat a pupil position, and then the light flux passes through a vibrationreduction optical system 2 and forms an image once again on an imageplane of an imaging element 1. Both the incidence angle and the exitangle of the light flux are ω. Here, the direction of a light ray, whichpasses, in a direction perpendicular to a principal plane, through aprincipal point in a case in which an image pickup optical system isregard as a single lens (composite lens), is defined as an optical axisof the image pickup optical system. In addition, in FIG. 1A and FIG. 1B,it is assumed that the optical axis of the image pickup optical systemagrees with the optical axis of the vibration reduction optical system2. In this case, as illustrated in FIG. 1A, when no blur occurs in theimage pickup apparatus, a y-axis position of the optical axis at thepupil position of the image pickup optical system agrees with a y-axisposition of an image plane center (which agrees with an image center) ofthe imaging element 1. Accordingly, light (principal light ray), whichpasses through the optical axis of the image pickup optical system, isincident on the image plane center PO of the imaging element 1 throughthe optical axis of the vibration reduction optical system 2. On theother hand, as illustrated in FIG. 1B, if image blur of angle θ occursin the image pickup apparatus, a displacement occurs between the y-axisposition of the optical axis at the pupil position of the image pickupoptical system and the y-axis position of the image plane center of theimaging element 1. Due to the magnitude of this displacement, the lightflux, which radiates from an identical object point of the subject,forms an image at an image-formation position on the imaging element 1,which is different from the image-formation position at the time when noblur occurs. Image blur occurs due to this displacement of theimage-formation position. In the meantime, such image blur occurs notonly due to an angular shake, but also due to a shift shake by which theimage pickup apparatus shifts in a direction parallel to the imageplane.

Blur suppression methods for suppressing image blur are mainlyclassified into an optical system shift type, an imaging element shifttype, and an electronic type. As illustrated in FIG. 2A, the opticalsystem shift-type blur suppression process is a process of suppressingblur by driving the vibration reduction optical system 2, which is apart of the image pickup optical system, in a plane perpendicular to theoptical axis of the image pickup optical system in accordance with adetected blur. Specifically, in the optical system shift-type blursuppression process, the image-formation position of the light flux ismoved to P1, without the image plane center PO being moved. Asillustrated in FIG. 2B, the imaging element shift-type blur suppressionprocess is a process of suppressing blur by driving the imaging element1 in the plane perpendicular to the optical axis of the image pickupoptical system in accordance with the detected blur. Specifically, inthe imaging element shift-type blur suppression process, the image planecenter PO is moved to P1. The electronic-type blur suppression processis a process of suppressing blur by changing a cropping range of aphotographed image (in the plane perpendicular to the optical axis) inaccordance with the detected blur. Specifically, in the electronic-typeblur suppression process, as illustrated in FIG. 2C, only the croppingrange of the photographed image is changed, without the image planecenter PO or image-formation position being moved.

FIG. 3A illustrates a photographed image in which no image blur occurs.If the optical axis of the image pickup optical system is aligned withthe subject, the position of the subject O on the image plane agreeswith the position of the image center PO when no blur occurs. Inaddition, an intersection position between the optical axis of the imagepickup optical system and the image plane agrees with the image centerPO. In the case of either barrel distortion or pincushion distortion,the distortion occurs in point-symmetry with respect to the optical axisof the image pickup optical system as the center of symmetry.Accordingly, in the case of FIG. 3A, distortion D, which affects aphotographed image, has a point-symmetric shape with respect to theimage center PO as the center of symmetry.

FIG. 3B illustrates a photographed image in which image blur occurs.Since the optical axis of the image pickup optical system deviates fromthe subject due to a shake of the image pickup apparatus, the positionof the subject O on the image plane moves from the position of the imagecenter PO. On the other hand, when the blur suppression process is notexecuted, the intersection position between the optical axis of theimage pickup optical system and the image plane agrees with the imagecenter PO. Accordingly, in the case of FIG. 3B, distortion D, whichaffects a photographed image, has a point-symmetric shape with respectto the image center PO as the center of symmetry.

FIG. 3B is a view illustrating the photographed image in which imageblur occurs, and FIG. 3C illustrates a photographed image after theimaging element shift-type or electronic-type blur suppression processwas applied to the image blur of FIG. 3B. By the blur suppressionprocess, the image center PO is aligned with the position of the subjectO. On the other hand, the intersection position P1 between the opticalaxis of the image pickup optical system and the image plane deviatesfrom the image center PO. Accordingly, in the case of FIG. 3C,distortion D, which affects a photographed image, has anon-point-symmetric shape. If the distortion D of FIG. 3C and thedistortion D of FIG. 3A and FIG. 3B are compared, the shape of thedistortion D of FIG. 3C appears as if the shape was deformed by the blursuppression process.

On the other hand, FIG. 4 illustrates a photographed image after theoptical system shift-type blur suppression process was applied to theimage blur of FIG. 3B. As illustrated in FIG. 4, in the case of theoptical system shift-type blur suppression process, the position PO,which is the intersection between the light ray passing through theoptical axis of the image pickup optical system 21 and the image plane,is aligned with the position of the subject O. As described above, thedistortion occurs in point-symmetry with respect to the optical axis ofthe image pickup optical system as the center of symmetry. Thus, thedistortion D, which occurred, prior to the blur suppression process, inpoint-symmetry with respect to an intersection P2 as the center ofsymmetry between the optical axis of the image pickup optical system 21and the image plane before the driving of the vibration reductionoptical system 2, will occur in non-point symmetry with respect to theintersection PO as the center of symmetry between the light (principallight ray) passing through the optical axis of the image pickup opticalsystem 21 and the image plane after the driving of the vibrationreduction optical system 2. If the distortion D of FIG. 4 and thedistortion D of FIG. 3A or FIG. 3B are compared, the shape of thedistortion D of FIG. 4 appears as if the shape was deformed by the blursuppression process.

As a method for exactly correcting the shape variation of the distortiondue to the blur suppression process, a method is thinkable, whichcorrects distortion by taking into account a variation of the shape ofthe distortion. In normal distortion correction, the relationshipbetween an ideal image height Y (image height after correction) and anactual image height Y′ (image height before correction) is predefined asinformation (distortion correction information) for correctingdistortion. This relationship is defined by, for example, an approximatepolynomial expression such as equation (1) below. In addition, in theactual process, distortion correction is executed by coordinateconversion using the predefined relationship. Specifically,corresponding coordinates between an image before correction and animage after correction are calculated by using the definitionalequation, and correction is made by rearranging the pixels in the imagebefore correction in accordance with the corresponding coordinates.Y=D0+D1Y′+D2Y′ ² +D2Y′ ³+  equation (1)

In the distortion correction on the photographed image after the imagingelement shift-type or electronic-type blur suppression process, it ispossible to execute correction including correction of a change indistortion shape by usual distortion correction, in which a displacementamount between the image center and the optical axis of the image pickupoptical system is taken into account. Specifically, distortioncorrection is executed by using the above equation (1), with the pixelposition in the image, which corresponds to the optical axis of theimage pickup optical system, being set as a reference position.

On the other hand, since a shape variation of distortion due todecentering of the vibration reduction optical system and a shapevariation of distortion due to a displacement between the image centerand the optical axis of the image pickup optical system are different inthe principle of occurrence, uncorrected distortion remains even ifusual distortion correction is executed by taking into account adisplacement amount between the image center and the optical axis of theimage pickup optical system.

Here, although the shape variation of distortion due to the decenteringof the vibration reduction optical system and the shape variation ofdistortion due to the displacement between the image center and theoptical axis of the image pickup optical system are different in theprinciple of occurrence, these shape variations have generally similarcharacteristics. FIG. 5 is a view illustrating an example of therelationship between the shape variation of distortion due to thedecentering of the vibration reduction optical system and the shapevariation of distortion due to the displacement between the image centerand the optical axis of the image pickup optical system. Here, in FIG.5, for easier understanding of only the variation in distortion shape,it is assumed that the subject that is an object of photography is asubject of a lattice pattern. In addition, a left part of FIG. 5illustrates distortion shapes in photographed images at times when thesubject was photographed in the state in which the image pickup system(the image pickup apparatus in the state in which the image pickupoptical system is mounted) was shifted by 0 mm in vertical, 0.05 mm invertical and 0.1 mm in vertical and the imaging element was driven by 0mm in vertical, 0.05 mm in vertical and 0.1 mm in vertical so as tocorrect image blurs due to the shifts of the image pickup system. Aright part of FIG. 5 illustrates distortion shapes in photographedimages at times when the subject was photographed in the state in whichthe image pickup system (the image pickup apparatus in the state inwhich the image pickup optical system is mounted) was shifted by 0 mm invertical, 0.05 mm in vertical and 0.1 mm in vertical, which are the sameconditions as in the left part of FIG. 5, and the vibration reductionoptical system was driven by 0 mm in vertical, 0.05 mm in vertical and0.1 mm in vertical so as to correct image blurs due to the shifts of theimage pickup system. Incidentally, for the purpose of simpledescription, it is assumed that when the vibration reduction opticalsystem was driven by 1 mm, the image on the image plane moves by 1 mm.Depending on the configuration of the vibration reduction opticalsystem, a driving amount d of the vibration reduction optical system anda movement amount m on the image plane do not necessarily agree, andhave a proportional relationship as indicated by equation (2) below. InFIG. 5, it is thought that an image plane movement sensitivity s inequation (2) is 1. At this time, a driving amount, which is necessaryfor suppressing the same blur, is equal between the imaging element andthe vibration reduction optical system.m=s×d  equation (2)where s=(1−β2)×β3  equation (3)(β2: a magnification of the vibration reduction optical system, β3: amagnification of a group in rear of the vibration reduction opticalsystem of the image pickup optical system).

As is understood from FIG. 5, even if distortion shapes in the states inwhich the imaging element and the vibration reduction optical systemwere driven by the same amount are compared, both distortion shapes donot agree. However, in the case of FIG. 5, distortion shapes in both thestate, in which the vibration reduction optical system was driven by0.05 mm, and the state, in which the imaging element was driven by 0.1mm, are similar.

Accordingly, when a photographed image in a state in which the vibrationreduction optical system was driven by 0.05 mm is to be corrected, ifthere is a “mechanism that can correct distortion, which occurs inpoint-symmetry with respect to a position where the optical axis of theimage pickup is focused, by taking into account a displacement betweenthe image center and the position where the optical axis of the imagepickup is focused”, such as equation (1), it should suffice if 0.1 mm isgiven to this mechanism as a displacement amount between the imagecenter and the optical axis center. Thereby, it is possible to generallycorrect the shape variation of distortion (non-point-symmetrization ofthe distortion shape) due to the driving of the vibration reductionoptical system.

In a concrete process, for example, a correlation between the drivingamount of a vibration reduction optical system and the driving amount ofan imaging element, which are similar in shape of distortion on an imageplane, is predefined. When the vibration reduction optical system wasdriven, the driving amount of the vibration reduction optical system isconverted to a corresponding driving amount of the imaging element. Inaccordance with the driving amount after the conversion, for example,distortion correction based on equation (1) is executed. FIG. 6A andFIG. 6B illustrate examples of the correlation between the drivingamount of the vibration reduction optical system and the driving amountof the imaging element, which are similar in shape of distortion on theimage plane. FIG. 6A is an example in which the correlation is linear.In the case of the linear correlation, when distortion correction isexecuted, conversion is executed by multiplying the driving amount ofthe vibration reduction optical system by a predetermined coefficient.On the other hand, FIG. 6B is an example in which the correlation isnonlinear. In the case of the nonlinear correlation, an approximateexpression representing the curve of the nonlinear correlation ispredefined. In addition, when distortion correction is executed, thedriving amount of the vibration reduction optical system is converted byusing the approximate expression. The relationship of FIG. 6B isapproximated by, for example, a quadratic expression. However, it is notalways necessary that the relationship of FIG. 6B be approximated by thequadratic expression. Although the relationship of FIG. 6B may beapproximated by an equation of a proper degree, that is, a cubicequation or a higher-degree equation. In addition, the relationship maybe approximated by a proper equation, aside from a polynomialexpression.

Specifically, as described above, a function (reference positionconversion function) is obtained, which indicates a correlation betweenthe shape of distortion on the image plane of the imaging element, whichcorresponds to the driving amount of the vibration reduction opticalsystem, and the shape of distortion on the image plane of the imagingelement, which corresponds to the displacement amount between theoptical axis of the image pickup optical system and the image center ofthe photographed image. By using this reference position conversionfunction, the driving amount of the vibration reduction optical systemis converted to the driving amount of the imaging element. By using theconverted result, distortion correction is executed. Thereby, the imagepickup apparatus can execute distortion correction with high precisionby the simple method.

[First Embodiment]

FIG. 7 and FIG. 8 are views illustrating a configuration example of animage pickup system 3 according to a first embodiment. FIG. 7 is a viewillustrating an external appearance of an interchangeable lens 4 and acamera body 5 of the image pickup system 3. FIG. 8 is a viewillustrating a configuration example of a control system of the imagepickup system 3. The image pickup system 3 includes the interchangeablelens 4 and camera body 5. The interchangeable lens 4 and camera body 5are communicably connected via lens mounts 6. The lens mounts 6 areformed on the interchangeable lens 4 and camera body 5, respectively. Bythe lens mounts 6 being engaged, the interchangeable lens 4 and camerabody 5 are fixed, and the interchangeable lens 4 and camera body 5 areconnected in the communicable state.

In the description below, the left-and-right direction of the camerabody 5 is defined as an X direction, and the up-and-down directionthereof is defined as a Y direction. The image plane of the imagingelement 12 is formed in parallel to the X direction and Y direction.Here, the right direction in the X direction in a case where the camerabody 5 is viewed from the subject side is defined as a (+) direction,and the left direction in this case is defined as a (−) direction. Theupward direction in the Y direction is defined as a (+) direction, andthe downward direction in the Y direction is defined as a (−) direction.In addition, the optical axis direction of the image pickup opticalsystem 21 of the interchangeable lens 4 is defined as a Z direction. Thesubject side in the Z direction is defined as a (+) direction, and theside opposite to the subject side is defined as a (−) direction.

Furthermore, a rotational movement about the X direction, which is thehorizontal direction of the imaging plane of the imaging element 12, isreferred to as a pitch-directional rotational movement. A rotationalmovement about the Y direction, which is the vertical direction of theimaging plane, is referred to as a yaw-directional rotational movement.A rotational movement about the Z direction, which is the optical axisof the image pickup optical system 21, is referred to as aroll-directional rotational movement. Incidentally, the rotation in thedirection of each arrow in FIG. 7 is referred to as a (+) directionalrotation, and the rotation in the opposite direction is referred to a(−) directional rotation. The above-described relationship between thepositive (+) and negative (−) is determined by the specifications of anangular velocity sensor 23, and this relationship may be reversed.

The interchangeable lens 4 is mounted on the camera body 5 via the lensmounts 6. When the interchangeable lens 4 was mounted on the camera body5, the interchangeable lens 4 operates in accordance with the control ofthe camera body 5. The interchangeable lens 4 includes an image pickupoptical system 21, a lens control unit (LCU) 22, angular velocity sensor23, and an optical system driving unit 24.

The image pickup optical system 21 is an imaging lens which forms animage on the image plane. The image pickup optical system 21 forms animage of a light flux from a subject (not shown) onto the image plane ofthe imaging element 12 of the camera body 5. The image pickup opticalsystem 21 includes, for example, an optical system (zooming opticalsystem) 21 a for varying a focal distance of the image pickup opticalsystem 21, an optical system (focusing optical system) 21 b for changinga focus state of the image by moving a focus position, and a vibrationreduction optical system 21 c which is driven in a directionperpendicular to the optical axis of the image pickup optical system 21.

The LCU 22 is a controller which includes, a processer for example a CPU(Central Processing Unit) and a memory, and controls the operation ofthe interchangeable lens 4. For example, the LCU 22 controls the drivingof the lenses and aperture of the image pickup optical system 21 inaccordance with an instruction from a system controller 13 of the camerabody 5.

The LCU 22 stores in the memory the information (first lens information)which is indicative of optical characteristics of the image pickupoptical system 21 of the interchangeable lens 4. The LCU 22 stores inthe memory, for example, as the first lens information, a focal distanceof the image pickup optical system 21, a position (zoom position) atwhich the zooming optical system 21 a can be driven, a position (focusposition) at which the focusing optical system 21 b can be driven,distortion correction information for correcting distortion of the imagepickup optical system 21, and a reference position conversion function.The distortion correction information and reference position conversionfunction are constituted, for example, for each of combinations betweenthe zoom position and the focus position. The LCU 22 supplies the firstlens information, which is stored in the memory, to the camera body 5 inaccordance with an instruction from the system controller 13.

In addition, the LCU 22 recognizes the focus position, the zoomposition, and the driving amount of the vibration reduction opticalsystem 21 c, and supplies the recognized information (second lensinformation) to the camera body 5.

The angular velocity sensor 23 detects, as an angular velocity signal, arotational movement which occurs in accordance with the attitude of theinterchangeable lens 4 that is mounted on the camera body 5. The angularvelocity sensor 23 detects, for example, the above-describedyaw-directional and pitch-directional rotational movements, andgenerates angular velocity signals. The angular velocity sensor 23includes an angular velocity sensor 23 a which detects theyaw-directional rotational movement, and an angular velocity sensor 23 bwhich detects the pitch-directional rotational movement.

The optical system driving unit 24 drives the zooming optical system 21a, focusing optical system 21 b and vibration reduction optical system21 c of the image pickup optical system 21 in accordance with thecontrol of the LCU 22. The optical system driving unit 24 varies thefocal distance of the image pickup optical system 21 by driving thezooming optical system 21 a and changing the position of the zoomingoptical system 21 a on the optical system. In addition, the opticalsystem driving unit 24 changes the focus position of the image pickupoptical system 21 by driving the focusing optical system 21 b andchanging the position of the focusing optical system 21 b on the opticalsystem. Furthermore, the optical system driving unit 24 suppresses imageblur by changing the position of the image, which is formed on the imageplane by the image pickup optical system 21, by driving the vibrationreduction optical system 21 c in the direction perpendicular to theoptical axis. The optical system driving unit 24 functions as a blurcorrection actuator.

The LCU 22 functions as a blur amount acquisition unit (blur amountdetection sensor) which calculates the blur amount of the image pickupsystem 3, based on the angular velocity signal detected by the angularvelocity sensor 23. In the present embodiment, the LCU 22 calculates,based on the angular velocity signal, the blur amount of the imagepickup optical system 21 as the blur amount of the image pickup system3. Specifically, the blur amount is a yaw-directional rotationalmovement of the optical axis of the image pickup optical system 21, anda pitch-directional rotational movement of the optical axis of the imagepickup optical system 21. Based on the blur amount and the opticalcharacteristics of the image pickup optical system 21, the LCU 22calculates the movement amount (displacement amount) of the image on theimage plane. Based on the calculated displacement amount, the LCU 22tells the driving amount of the vibration reduction optical system 21 cto the optical system driving unit 24, and thereby the displacement ofthe image on the image plane can be canceled.

The camera body 5 includes a shutter 11, imaging element 12, systemcontroller 13, and an operation unit 14.

The shutter 11 is a mechanism which is provided between the image pickupoptical system 21 and imaging element 12, and adjusts the amount oflight which passes through the image pickup optical system 21 and isincident on the imaging element 12. The shutter 11 is, for example, afocal plane shutter. The shutter 11 controls an exposure time which is atime in which light is incident on the imaging element 12, byopening/closing a shutter curtain.

The imaging element 12 is provided in rear of the image pickup opticalsystem 21, that is, in the inner side of the housing of the camera body5. The imaging element 12 includes an image plane which is composed suchthat a plurality of imaging pixels, which photoelectrically convertlight and accumulate electric charge, are arranged. The imaging element12 is composed of, for example, a complementary metal oxidesemiconductor (CMOS) image sensor, or some other imaging element. Theimaging element 12 converts an image (subject image), which is convergedvia the image pickup optical system 21 and formed on the image plane, toan electric signal corresponding to the light amount, thereby generatingan image signal. The imaging element 12 supplies the image signal to thesystem controller 13 in accordance with a control signal from the systemcontroller 13.

The system controller 13 is a controller which includes, a processer,for example a CPU and a memory, and controls the operation of the camerabody 5. In addition, the system controller 13 includes a communicationunit which communicates with the LCU 22 of the interchangeable lens 4via the lens mounts 6. The communication unit is composed of, forexample, a transmission circuit and a reception circuit. In addition,the communication unit transmits/receives control signals andinformation signals to/from the LCU 22 of the interchangeable lens 4,thereby controlling the operation of the interchangeable lens 4.

For example, the system controller 13 transmits, from the communicationunit to the LCU 22 of the interchangeable lens 4, control signals of,for example, an instruction to drive the aperture for exposureadjustment, an instruction of the focus position, and an instruction ofthe zoom position. In addition, the system controller 13 executescontrol of image display on display means (not shown), recording ofimage files in a recording device (not shown), control to switch theoperation mode in accordance with the operation of the operation unit14, and control to start or end an imaging operation.

In addition, the system controller 13 reads out an image signal from theimaging element 12, executes signal processing on the read-out imagesignal, and acquires image data (photographed image). Further, thesystem controller 13 applies various signal processes to thephotographed image. These signal processes include the above-describeddistortion correction. For this purpose, the system controller 13acquires the above-described first lens information and second lensinformation by the reception circuit of the communication unit, andcorrects the distortion, based on the acquired first lens informationand second lens information.

The operation unit 14 includes operation members which are operated by auser. For example, the operation unit 14 includes, as the operationmembers, a release button and a movie recording button. The releasebutton is a button for causing the camera body 5 to execute a stillimage photography process. In addition, the movie recording button is abutton for causing the camera body 5 to execute a movie recordingprocess. Besides, the operation unit 14 may include, as the operationmember, a button for changing the operation mode of the camera body 5 orchanging various settings such as exposure control. For example, theoperation unit 14 may include, as the operation member, a button forchanging the setting of execution/non-execution of distortioncorrection.

Next, a process in the inside of the system controller 13 will bedescribed. FIG. 9 is a block diagram illustrating, as blocks, functionswhich the system controller 13 includes. The system controller 13includes an image generator 131, a memory 132, a reference positioncalculator 133, and an image processor 134.

The image generator 131 converts an image signal, which was read fromthe imaging element 12, to image data (photographed image) which can besubjected to image processing. The image generator 131 supplies theconverted image data to the memory 132.

The memory 132 is a storage area for storing data. The memory 132 storesimage data which was supplied from the image generator 131. In addition,the memory 132 stores the above-described first lens information andsecond lens information.

The reference position calculator 133 calculates a displacement amountbetween the optical axis of the image pickup optical system 21 and theimage center of the photographed image, based on the first lensinformation and second lens information stored in the memory 132. Forexample, the reference position calculator 133 recognizes the opticalcharacteristics of the image pickup optical system 21 and the drivingamount of the vibration reduction optical system 21 c, based on thefirst lens information and second lens information. To be more specific,the reference position calculator 133 recognizes the focal distance ofthe image pickup optical system 21 and the driving amount of thevibration reduction optical system 21 c, based on the first lensinformation and second lens information. The reference positioncalculator 133 calculates the above-described displacement amount, basedon the recognized focal distance of the image pickup optical system 21and the recognized driving amount of the vibration reduction opticalsystem 21 c.

Furthermore, the reference position calculator 133 converts thecalculated displacement amount, based on the first lens information andsecond lens information. The reference position calculator 133recognizes the focus position and zoom position of the image pickupoptical system from the second lens information, and specifies onereference position conversion function from the first lens informationin accordance with the recognized result. The reference positioncalculator 133 converts the above-described displacement amount by usingthe specified reference position conversion function, therebycalculating a converted displacement amount. Specifically, the referenceposition calculator 133 functions as a displacement amount conversionunit which calculates the displacement amount and converts thedisplacement amount. The reference position calculator 133 calculates areference position for distortion correction in accordance with thecalculated converted displacement amount.

For example, when the shape of distortion on the image plane, whichcorresponds to the driving amount of the vibration reduction opticalsystem 21 c, and the shape of distortion on the image plane, whichcorresponds to the displacement amount between the optical axis and theimage center, have a relation of a linear function with a coefficient α,the reference position conversion function can be expressed by:Converted displacement amount=displacement amount×α  equation (4)

The image processor 134 executes distortion correction of thephotographed image, based on the first lens information and thereference position. For example, the image processor 134 executesdistortion correction of the photographed image, based on the distortioncorrection information of the first lens information, with the referenceposition being set as the center of distortion correction.

As described above, the system controller 13 executes distortioncorrection, based on the converted displacement amount, which iscalculated by converting, by the preset reference position conversionfunction, the displacement amount between the optical axis and the imagecenter of the photographed image, the displacement amount beingcalculated based on the calculated focal distance of the image pickupoptical system 21 and the calculated driving amount of the vibrationreduction optical system 21 c. Thereby, the system controller 13 canexecute distortion correction by approximating the shape of distortionon the image plane, which corresponds to the driving amount of thevibration reduction optical system 21 c, as the shape of distortion onthe image plane, which corresponds to the displacement amount betweenthe optical axis and the image center of the photographed image.

Next, a process in the interchangeable lens 4 will be described. FIG. 10is an explanatory view illustrating an example of a configuration fordriving the vibration reduction optical system 21 c of the opticalsystem driving unit 24. The optical system driving unit 24 includes, forexample, a movable unit 244 which operates in interlock with thevibration reduction optical system 21 c; a support unit 243 whichsupports the movable unit 244; and an actuator 241 and an actuator 242which drive the movable unit 244.

The actuator 241 and actuator 242 drive the movable unit 244 indirections perpendicular to the optical axis of the image pickup opticalsystem 21 in accordance with the control of the LCU 22. Each of theactuator 241 and actuator 242 includes, for example, an electromagneticlinear motor (e.g. voice coil motor) which is composed of anelectromagnetic coil provided in the movable unit 244, and a fixedmagnet which is provided in the support unit 243 and is magneticallyconnected to the electromagnetic coil.

The actuator 241 and actuator 242 are configured to drive the movableunit 244 in directions perpendicular to the optical axis of the imagepickup optical system 21, by an interaction of a magnetic fieldoccurring between the electromagnetic coil and fixed magnet, when adriving current from the LCU 22, which corresponds to the driving amountof the vibration reduction optical system 21 c (the movement amount anddirection from the position where the optical axis of the image pickupoptical system agrees with the optical axis of the vibration reductionoptical system 21 c), was caused to flow through the electromagneticcoil that constitutes the electromagnetic linear motor. For example, theactuator 241 is configured to drive the movable unit 244 in the Xdirection by the interaction of the magnetic field. In addition, forexample, the actuator 242 is configured to drive the movable unit 244 inthe Y direction by the interaction of the magnetic field.

FIG. 11 is a block diagram illustrating, as blocks, functions which theLCU 22 includes. The LCU 22 includes an analog-to-digital converter(ADC) 221 a, an ADC 221 b, a correction amount calculator 222 a, acorrection amount calculator 222 b, a driving amount calculator 223, anactuation driver 224 a, an actuation driver 224 b, a memory 225, and acommunication unit 226.

The ADC 221 a converts a yaw-directional angular velocity signal, whichis output from the angular velocity sensor 23 a, to a digital value. TheADC 221 b converts a pitch-directional angular velocity signal, which isoutput from the angular velocity sensor 23 b, to a digital value.

The correction amount calculator 222 a calculates a Y-directional imageblur amount (displacement amount) occurring on the image plane, based onthe yaw-directional angular velocity signal and the opticalcharacteristics of the image pickup optical system 21. The correctionamount calculator 222 b calculates an X-directional image blur amount(displacement amount) occurring on the image plane, based on thepitch-directional angular velocity signal and the opticalcharacteristics of the image pickup optical system 21. FIG. 12 is anexplanatory view for explaining the operation of the correction amountcalculator 222 a and correction amount calculator 222 b. Specifically,each of the correction amount calculator 222 a and correction amountcalculator 222 b multiplies an input digital angular velocity signal byan optical characteristic OP corresponding to the focal distance of theimage pickup optical system 21, and integrates the multiplied value,thereby calculating a displacement amount as a correction amount.

For example, when the focal distance is f and the correction sensitivityof the vibration reduction optical system 21 c is K, the opticalcharacteristic OP is expressed by:Optical characteristic OP=f/K  equation (5)

In order to use the optical characteristic OP for the calculation of thedisplacement amount, the LCU 22 detects the focal distance f byperiodically detecting the zoom position of the image pickup opticalsystem 21.

The correction sensitivity K is a ratio (variation ratio) of thedisplacement amount of the image on the image plane to the drivingamount of the vibration reduction optical system 21 c at a certain focaldistance f.

In the correction in the interchangeable lens 4, the displacement amountof the image on the image plane of the imaging element 12 does not agreewith the driving amount of the vibration reduction optical system 21 c.Thus, using the above equation (5), the displacement amount of the imageon the image plane is converted to the driving amount of the vibrationreduction optical system 21 c, based on the correction sensitivity K.

As described above, the correction amount calculator 222 a calculatesthe Y-directional displacement amount occurring on the image plane, bymultiplying the yaw-directional angular velocity by the opticalcharacteristic OP. In addition, the correction amount calculator 222 bcalculates the X-directional displacement amount occurring on the imageplane, by multiplying the pitch-directional angular velocity by theoptical characteristic OP.

The driving amount calculator 223 calculates the X-directional andY-directional driving amounts of the vibration reduction optical system21 c, based on the X-directional and Y-directional displacement amountscalculated by the correction amount calculator 222 a and correctionamount calculator 222 b.

The actuation driver 224 a outputs to the optical system driving unit 24a driving pulse signal which has a current waveform corresponding to theX-directional driving amount of the vibration reduction optical system21 c. In addition, the actuation driver 224 b outputs to the opticalsystem driving unit 24 a driving pulse signal which has a currentwaveform corresponding to the Y-directional driving amount of thevibration reduction optical system 21 c.

The memory 225 is a memory which stores the first lens information. Forexample, the memory 225 stores the focal distance of the image pickupoptical system 21, the zoom position of the zooming optical system 21 a,the focus position of the focusing optical system 21 b, the distortioncorrection information for correcting distortion of the image pickupoptical system 21, and the reference position conversion function. Thememory 225 may additionally store the second lens information. Forexample, the memory 225 stores, as the second lens information, thepresent focus position and zoom position of the image pickup opticalsystem 21, and the driving amount of the vibration reduction opticalsystem 21 c, which were recognized by the LCU 22.

The communication unit 226 communicates with the camera body 5 via thelens mounts 6. Thereby, the communication unit 226 receives, from thecamera body 5, a notification of the start and end of blur correction bythe vibration reduction optical system 21 c, a control signal forexposure adjustment, an instruction of the focus position, and aninstruction of the zoom position. The communication unit 226 transmitsthe first lens information and second lens information, for example,responding to a request from the system controller 13 of the camera body5.

Next, a description will be given of the operation relating todistortion correction of the camera body 5 and interchangeable lens 4 ofthe image pickup system 3. FIG. 13 is a flowchart illustrating anexample of the operation relating to distortion correction of the camerabody 5 and interchangeable lens 4.

When the camera body 5 acquired a photographed image by the imagingelement 12, the camera body 5 determines whether the distortioncorrection is effective or not. If the distortion correction iseffective, the camera body 5 executes the distortion correction. Thecamera body 5 first determines whether the present time is immediatelyafter the mounting of the interchangeable lens 4 (step S11). If thecamera body 5 determines that the present time is immediately after themounting of the interchangeable lens 4 (step S11, YES), the camera body5 then receives and acquires the reference position conversion functionfrom the interchangeable lens 4 (step S12).

FIG. 14 is an explanatory view illustrating an example of the referenceposition conversion function. The reference position conversion functionis a function which is set for each of combinations between the zoomposition of the zooming optical system 21 a and the focus position ofthe focusing optical system 21 b. For example, the camera body 5acquires from the interchangeable lens 4 the first lens informationincluding the reference position conversion function. In addition, forexample, the camera body 5 may request the interchangeable lens 4 totransmit the reference position conversion function. Incidentally, whenthe image pickup optical system 21 does not include the zooming opticalsystem 21 a, the reference position conversion function may be formedfor each of focus positions.

In addition, if the camera body 5 determines that the present time isnot immediately after the mounting of the interchangeable lens 4 (stepS11, NO), the camera body 5 then goes to the process of step S13.

The camera body 5 determines whether camera shake correction in theinterchangeable lens 4 is effective or not (step S13). For example, ifthe camera body 5 determines that the camera shake correction in theinterchangeable lens 4 is effective, the camera body 5 may transmit acontrol signal to the interchangeable lens 4 so as to execute camerashake correction.

If the camera body 5 determines that the camera shake correction in theinterchangeable lens 4 is effective (step S13, YES), the camera body 5acquires the driving amount of the vibration reduction optical system 21c, the zoom position and the focus position from the interchangeablelens 4 (step S14). Specifically, the camera body 5 acquires the secondlens information from the interchangeable lens 4. For example, thecamera body 5 may request the interchangeable lens 4 to transmit thesecond lens information. In addition, if the camera body 5 determinesthat the camera shake correction in the interchangeable lens 4 is noteffective (step S13, NO), the camera body 5 goes to the process of stepS16.

The camera body 5 calculates a reference position, based on the acquiredzoom position, focus position and driving amount of the vibrationreduction optical system 21 c (step S15). For example, based on theacquired zoom position and focus position, the camera body 5 specifiesone reference position conversion function from among the referenceposition conversion functions for the respective combinations betweenthe zoom position and focus position. In addition, the camera body 5calculates a displacement amount, based on the driving amount of thevibration reduction optical system 21 c and the zoom position (the focaldistance of the image pickup optical system 21). Furthermore, the camerabody 5 calculates a converted displacement amount by converting thedisplacement amount by the reference position conversion function. Basedon the converted displacement amount, the camera body 5 calculates thereference position which is used for the distortion correction.

The camera body 5 executes distortion correction of the photographedimage, based on the distortion correction information of the imagepickup optical system 21 and the reference position that was calculatedfrom the converted displacement (step S16). In the meantime, when thecamera shake correction in the interchangeable lens 4 is effective, thecamera body 5 executes the distortion correction by using the calculatedreference position as a reference. On the other hand, when the camerashake correction in the interchangeable lens 4 is not effective, thecamera body 5 executes the distortion correction by using, as areference, the image formation position which exists on the image planeof the imaging element 12 and corresponds to the optical axis of theimage pickup optical system 21.

The interchangeable lens 4 transmits the reference position conversionfunction to the camera body 5 (step S17). For example, theinterchangeable lens 4 may be configured to transmit the referenceposition conversion function in response to a request for the referenceposition conversion function from the camera body 5, or may beconfigured to transmit the reference position conversion function when aconnection to the camera body 5 was detected.

The interchangeable lens 4 detects the blur amount of the image pickupsystem 3, and calculates the driving amount of the vibration reductionoptical system 21 c (step S18). The interchangeable lens 4 drives thevibration reduction optical system 21 c in accordance with thecalculated driving amount. In the meantime, the interchangeable lens 4may be configured to execute the process of step S18 when theinterchangeable lens 4 received from the camera body 5 the controlsignal which instructs execution of the camera shake correction, or maybe configured to calculate the driving amount of the vibration reductionoptical system 21 c regardless of the reception/non-reception of thiscontrol signal.

The interchangeable lens 4 detects the position of the zooming opticalsystem 21 a of the image pickup optical system 21 and the position ofthe focusing optical system 21 b of the image pickup optical system 21,and acquires the zoom position and focus position (step S19). Theinterchangeable lens 4 generates the second lens information by theprocess of step S18 and step S19.

The interchangeable lens 4 transmits the driving amount of the vibrationreduction optical system 21 c, the zoom position and the focus positionto the camera body 5 (step S20). Specifically, the interchangeable lens4 transmits the second lens information to the camera body 5. Forexample, the interchangeable lens 4 may be configured to transmit thesecond lens information to the camera body 5 when the second lensinformation was requested by the camera body 5, or may be configured toperiodically transmit the second lens information to the camera body 5.Thereby, the interchangeable lens 4 transmits the information which isnecessary for the camera body 5 to execute the distortion correction.

The camera body 5 periodically executes the above step S11 to S16 whilephotographed images are being acquired. For example, the camera body 5executes the series of process steps of the above step S11 to S16, eachtime a photographed image is acquired. Thereby, the camera body 5 canacquire the second lens information for each of the photographed images.As a result, the camera body 5 can acquire the information which isnecessary for the distortion correction of each photographed image.

According to the above-described embodiment, the image pickup system 3sets the reference position of distortion correction, based on theconverted displacement amount, which is calculated by converting, by thepreset reference position conversion function, the displacement amountbetween the optical axis and the image center of the photographed image,the displacement amount being calculated based on the calculated focaldistance of the image pickup optical system 21 and the calculateddriving amount of the vibration reduction optical system 21 c, and theimage pickup system 3 executes the distortion correction. Thereby, theimage pickup system 3 can execute the distortion correction byapproximating the shape of distortion on the image plane, whichcorresponds to the driving amount of the vibration reduction opticalsystem 21 c, as the shape of distortion on the image plane, whichcorresponds to the displacement amount between the optical axis and theimage center of the photographed image. Specifically, the image pickupsystem 3 can execute, by the simple process, the distortion correctionwith consideration given to the shape of distortion on the image plane,which corresponds to the driving amount of the vibration reductionoptical system 21 c, and the shape of distortion on the image plane,which corresponds to the displacement amount between the optical axisand the image center of the photographed image.

In addition, according to the above-described embodiment, in the imagepickup system 3, the camera body 5 acquires in advance the first lensinformation including the reference position conversion function foreach of the combinations between the zoom position and focus position,and stores the first lens information in the memory 132, and the camerabody 5 acquires, from the interchangeable lens 4, the second lensinformation including the zoom position, focus position and drivingamount of the vibration reduction optical system 21 c in accordance withthe acquisition of the photographed image. Thereby, after acquiring thefirst lens information, the camera body 5 acquires the second lensinformation that is simple in structure, thus being able to executeproper distortion correction. Thereby, it is possible to reduce thecommunication capacity of the information which is necessary forexecuting the distortion correction between the camera body 5 and theinterchangeable lens 4.

Moreover, according to the above-described configuration, it is possibleto reduce, during photographing, the communication capacity of theinformation which is necessary for executing the distortion correctionbetween the camera body 5 and the interchangeable lens 4. Thus, whenimages are successively acquired in such cases as movie recording orlive view display, it is possible to prevent a processing delay due to adelay in communication between the interchangeable lens 4 and camerabody 5.

In particular, the reference position conversion function varies fromlens to lens. Thus, by providing the reference position conversionfunctions for lenses, the camera body 5 can acquire the information forexecuting proper distortion correction, no matter which kind of lens ismounted on the camera body 5. Moreover, since the camera body 5 is notrequired to store reference position conversion functions of allmountable lenses, the capacity of the memory that is used can bereduced.

[Second Embodiment]

Next, a second embodiment will be described. FIG. 15 is a viewillustrating a configuration of an image pickup system 3A according to asecond embodiment. Incidentally, the same structural parts as in thefirst embodiment are denoted by like reference numerals, and a detaileddescription thereof is omitted. The image pickup system 3A includes aninterchangeable lens 4 and a camera body 5A. The camera body 5A includesa shutter 11, an imaging element 12, a system controller 13A, anoperation unit 14, a blur correction microcomputer 15, an angularvelocity sensor 16, and an imaging element actuator 17.

The blur correction microcomputer 15 is a microcomputer which executescontrol relating to an image blur suppression process. The blurcorrection microcomputer 15 functions as a blur amount acquisition unitwhich calculates a blur amount of the image pickup system 3, based on anangular velocity signal which was detected by the angular velocitysensor 16. In the present embodiment, the blur correction microcomputer15 detects, based on the angular velocity signal, the blur amount of thecamera body 5 as the blur amount of the image pickup system 3.Specifically, the blur amount is rotational movements in the yawdirection, pitch direction and roll direction. The blur correctionmicrocomputer 15 calculates a displacement amount that is the amount ofimage blur occurring on the image plane of the imaging element 12, basedon the detection result of the blur amount and the opticalcharacteristics of the image pickup optical system 21, and calculatesthe driving amount of the imaging element 12 by the imaging elementactuator 17 in accordance with the displacement amount. The blurcorrection microcomputer 15 corrects the image blur by controlling theimaging element actuator 17 in a manner to actuate the image plane ofthe imaging element 12 in such a direction as to cancel the calculatedimage blur.

The angular velocity sensor 16 detects, as an angular velocity signal, arotational movement which occurs in accordance with the variation inattitude of the camera body 5A. The angular velocity sensor 16generates, for example, angular velocity signals corresponding torotational movements in the yaw directional, pitch directional and rolldirection. The angular velocity sensor 16 includes an angular velocitysensor 16 a which detects the yaw-directional rotational movement, anangular velocity sensor 16 b which detects the pitch-directionalrotational movement, and an angular velocity sensor 16 c which detectsthe roll-directional rotational movement.

The imaging element actuator 17 moves the image plane of the imagingelement 12 in a direction perpendicular to the optical axis of the imagepickup optical system 21 in accordance with the control of the blurcorrection microcomputer 15, thereby correcting the image blur on theimage plane, which occurs due to the variation in attitude of the camerabody 15A.

FIG. 16 is a block diagram illustrating, as blocks, functions which theblur correction microcomputer 15 includes.

The blur correction microcomputer 15 includes an analog-to-digitalconverter (ADC) 151 a, an ADC 151 b, an ADC 151 c, a correction amountcalculator 152 a, a correction amount calculator 152 b, a correctionamount calculator 152 c, a driving amount calculator 153, an actuationdriver 154 a, an actuation driver 154 b, an actuation driver 154 c, anda communication unit 155.

The ADC 151 a converts a yaw-directional angular velocity signal, whichis output from the angular velocity sensor 16 a, to a digital value. TheADC 151 b converts a pitch-directional angular velocity signal, which isoutput from the angular velocity sensor 16 b, to a digital value. TheADC 151 c converts a roll-directional angular velocity signal, which isoutput from the angular velocity sensor 16 c, to a digital value.

The correction amount calculator 152 a calculates an Y-directional imageblur amount (displacement amount) occurring on the image plane, based onthe yaw-directional angular velocity signal and the opticalcharacteristics of the image pickup optical system 21. The correctionamount calculator 152 b calculates a X-directional image blur amount(displacement amount) occurring on the image plane, based on thepitch-directional angular velocity signal and the opticalcharacteristics of the image pickup optical system 21. FIG. 17 is anexplanatory view for explaining the operation of the correction amountcalculator 152 a and correction amount calculator 152 b. Specifically,each of the correction amount calculator 152 a and correction amountcalculator 152 b multiplies an input digital angular velocity signal byan optical characteristic OP corresponding to the focal distance of theimage pickup optical system 21, multiplies the multiplied value by aratio of image blur correction (image blur correction ratio) in thecamera body 5A, and integrates the multiplied value, thereby calculatinga displacement amount as a correction amount.

The image blur correction ratio in the camera body 5A is indicative of aratio of image blur correction of the camera body 5A relative to theinterchangeable lens 4. The image blur correction ratio may be anarbitrary preset value such as 1:1, or may be set based on theperformance of image blur correction in the interchangeable lens 4 (e.g.the maximum value of the driving amount of the vibration reductionoptical system 21 c) and the performance of image blur correction in thecamera body 5A (e.g. the maximum value of the driving amount of theimaging element 12). When the image blur correction ratio is, forexample, 1:1, each of the correction amount calculator 152 a andcorrection amount calculator 152 b multiplies, by ½ as the image blurcorrection ratio, the value which was obtained by multiplying theangular velocity by the optical characteristic OP.

The correction amount calculator 152 c calculates a roll-directionalimage blur amount (displacement amount) occurring on the image plane,based on the roll-directional angular velocity signal. FIG. 18 is anexplanatory view for explaining an operation of the correction amountcalculator 152 c. Specifically, the correction amount calculator 152 ccalculates the displacement amount as the correction amount, byintegrating the angular velocity which is indicated by the inputroll-directional digital angular velocity signal.

The driving amount calculator 153 calculates the driving amount of theimaging element 12 by the imaging element actuator 17, based on thedisplacement amounts calculated by the correction amount calculator 152a, correction amount calculator 152 b and correction amount calculator152 c. Specifically, the driving amount calculator 153 calculates theX-directional and Y-directional driving amounts of the imaging element12 by the imaging element actuator 17, based on the X-directional andY-directional displacement amounts calculated by the correction amountcalculator 152 a and correction amount calculator 152 b. In addition,the driving amount calculator 153 calculates the roll-directionaldriving amount of the imaging element 12 by the imaging element actuator17, based on the roll-directional displacement amount calculated by thecorrection amount calculator 152 c.

The actuation driver 154 a outputs to the imaging element actuator 17 adriving pulse signal which has a current waveform corresponding to theX-directional driving amount of the imaging element 12 by the imagingelement actuator 17. The actuation driver 154 b outputs to the imagingelement actuator 17 a driving pulse signal which has a current waveformcorresponding to the Y-directional driving amount of the imaging element12 by the imaging element actuator 17. The actuation driver 154 coutputs to the imaging element actuator 17 a driving pulse signal whichhas a current waveform corresponding to the roll-directional drivingamount of the imaging element 12 by the imaging element actuator 17.

The communication unit 155 communicates with the system controller 13A,and acquires the optical characteristics of the image pickup opticalsystem 21. In addition, the communication unit 155 communicates with thesystem controller 13A, and acquires a control signal which instructs thestart and end of image blur correction.

Next, a process in the imaging element actuator 17 will be described.FIG. 19 is an explanatory view for explaining an example of theconfiguration of the imaging element actuator 17 for actuating theimaging element 12. The imaging element actuator 17 includes, forexample, a movable unit 175 which operates in interlock with the imagingelement 12; a support unit 174 which supports the movable unit 175; andan actuator 171, an actuator 172 and an actuator 173 which drive themovable unit 175.

The actuator 171 and actuator 172 drive the movable unit 175 in the Xdirection. The actuator 173 drives the movable unit 175 in the Ydirection. The actuator 171 and actuator 172 drive the movable unit 175in the roll direction by a difference in driving amount between theactuator 171 and actuator 172. Specifically, the actuator 171 andactuator 172 drive the movable unit 175 in the X direction and in theroll direction in accordance with the driving amount in the X directionand the driving amount in the roll direction. The actuator 173 drivesthe movable unit 175 in the Y direction in accordance with the drivingamount in the Y direction.

Each of the actuator 171, actuator 172 and actuator 173 includes, forexample, an electromagnetic linear motor (e.g. voice coil motor) whichis composed of an electromagnetic coil provided in the movable unit 175,and a fixed magnet which is provided in the support unit 174 and ismagnetically connected to the electromagnetic coil.

The actuator 171, actuator 172 and actuator 173 are configured to drivethe movable unit 175 in the X direction, Y direction and roll directionby an interaction of a magnetic field occurring between theelectromagnetic coil and fixed magnet, when a driving current from theblur correction microcomputer 15, which corresponds to the drivingamount of the imaging element 12, was caused to flow through theelectromagnetic coil that constitutes the electromagnetic linear motor.

The roll-directional driving amount (rotational movement angle) for theimaging element 12 is expressed by the equation below, if the rotationalmovement angle is a small value.Rotational movement angle=L·(movement amount of actuator 172−movementamount of actuator 171)   equation (7)where L is a constant which is determined by the arrangement of theactuator 171 and actuator 172 relative to the movable unit 175.

Next, a process in the system controller 13A will be described. FIG. 20is a block diagram illustrating, as blocks, functions which the systemcontroller 13A includes. The system controller 13A includes an imagegenerator 131, a memory 132, a reference position calculator 133A, andan image processor 134.

In addition, the system controller 13A includes a communication unitwhich is composed of a transmission circuit and a reception circuit. Thecommunication unit executes an operation of transmitting and receivingcontrol signals and information signals between the system controller13A and the LCU 22 of the interchangeable lens 4 via the lens mounts 6,and an operation of transmitting/receiving control signals andinformation signals to/from the communication unit 155 in the blurcorrection microcomputer 15. The reference position calculator 133Acalculates a reference position from the reference position conversionfunction stored in the memory 132, and the image movement amount on theimage plane, which corresponds to the driving amount of the imagingelement actuator 17.

As described above, in the present embodiment, the image blur correctionis executed in a divided manner between the camera body 5A andinterchangeable lens 4 at a ratio corresponding to the image blurcorrection ratio. Thus, in order to calculate the reference position,the correction amounts (driving amounts) of both the imaging elementactuator 17 and the optical system driving unit 24 are needed. However,the correction amount of the imaging element actuator 17 and thecorrection amount of the optical system driving unit 24 are determinedby the image blur correction ratio. Thus, if one of these correctionamounts can be calculated, the other correction amount can be estimated.

For example, if the image blur correction ratio is 1:1, the referenceposition calculator 133A calculates the reference position, based on thefollowing equation:Reference position=driving amount of imaging element actuator 17+drivingamount of imaging element actuator 17×α  equation (8)

Specifically, the reference position calculator 133A calculates thereference position, based on the sum between the driving amount of theimaging element actuator 17 and the estimated driving amount of thevibration reduction optical system 21 c.

In addition, as regards the LCU 22, the configuration of the correctionamount calculators 222 a and 222 b in the LCU 22 is different from thatin the first embodiment. FIG. 21 is an explanatory view for explainingthe operation of the correction amount calculators 222 a and 222 b inthe LCU 22 according to the second embodiment. Each of the correctionamount calculators 222 a and 222 b in the second embodiment multipliesan angular velocity by an optical characteristic OP corresponding to thefocal distance of the image pickup optical system 21, multiplies themultiplied value by the ratio of image blur correction (image blurcorrection ratio) in the interchangeable lens 4, and integrates themultiplied value, thereby calculating a displacement amount as acorrection amount. For this purpose, the LCU 22 acquires the image blurcorrection ratio in the interchangeable lens 4 from the systemcontroller 13.

Next, a description will be given of the operation relating todistortion correction of the camera body 5A and interchangeable lens 4of the image pickup system 3A according to the second embodiment. FIG.22 is a flowchart illustrating an example of the operation relating todistortion correction of the camera body 5A and interchangeable lens 4.Incidentally, since the processes of step S31 to step S33 correspond tostep S11 to step S13 in FIG. 13, a description thereof is omitted.

If the camera body 5A determines that the camera shake correction in theinterchangeable lens 4 is effective (step S33, YES), the camera body 5Aacquires the driving amount of the imaging element actuator 17, based onthe angular velocity detected by the angular velocity sensor 16, andestimates the driving amount of the vibration reduction optical system21 c, based on the driving amount of the imaging element actuator 17 andthe image blur correction ratio between the camera body 5A andinterchangeable lens 4 (step S34). Further, the camera body 5A drivesthe imaging element 12 by the imaging element actuator 17 in accordancewith the calculated driving amount.

The camera body 5A acquires the zoom position and the focus positionfrom the interchangeable lens 4 (step S35).

The camera body 5A calculates a reference position, based on theacquired zoom position, focus position and driving amount of the imagingelement actuator 17, and the estimated driving amount of the vibrationreduction optical system 21 c (step S36).

The camera body 5A executes distortion correction of the photographedimage, based on the distortion correction information of the imagepickup optical system 21 and the reference position (step S37).

The interchangeable lens 4 transmits the reference position conversionfunction to the camera body 5A (step S38).

The interchangeable lens 4 detects the blur amount of the image pickupsystem 3, and calculates the driving amount of the vibration reductionoptical system 21 c (step S39). The interchangeable lens 4 drives thevibration reduction optical system 21 c in accordance with thecalculated driving amount.

The interchangeable lens 4 detects the position of the zooming opticalsystem 21 a of the image pickup optical system 21 and the position ofthe focusing optical system 21 b of the image pickup optical system 21,and acquires the zoom position and focus position (step S40).

The interchangeable lens 4 transmits the zoom position and the focusposition to the camera body 5A (step S41). The camera body 5Aperiodically executes the above step S31 to S37 while photographedimages are being acquired. For example, the camera body 5A executes theabove step S31 to S37, each time a photographed image is acquired.Thereby, the camera body 5A can acquire the second lens information foreach of the photographed images. As a result, the camera body 5A canacquire the information which is necessary for the distortion correctionof each photographed image. In the meantime, the camera body 5A may beconfigured to acquire the first lens information from theinterchangeable lens 4 at a time of first communication after theconnection to the interchangeable lens 4, to periodically acquire thesecond lens information from the interchangeable lens 4, and to convertthe displacement amount between the optical axis and the image center ofthe photographed image by using the reference position conversionfunction, each time the photographed image is acquired by the imagingelement 12, thereby calculating the converted displacement amount.

According to the above-described second embodiment, in the image pickupsystem 3A, the camera body 5A does not acquire the driving amount of thevibration reduction optical system 21 c from the interchangeable lens 4.Instead, the camera body 5A estimates the driving amount of thevibration reduction optical system 21 c, based on the driving amount ofthe imaging element actuator 17, which the camera body 5A calculated,and the correction ratio between the camera body 5A and interchangeablelens 4. Thereby, the communication amount between the camera body 5A andinterchangeable lens 4 can be reduced, and the distortion correctionwith high precision can be executed.

In the meantime, in the above-described second embodiment, the camerabody 5A acquires the first lens information from the interchangeablelens 4, but the restriction to this configuration is unnecessary. Thecamera body 5A may include a communication unit which is connected to anetwork, and may be configured to acquire the first lens information bythis communication unit from a server which is connectable via thenetwork. In addition, the camera body 5A may be configured to prestorethe first lens information of a plurality of interchangeable lenses 4 inthe memory 132.

Additionally, in the second embodiment, the description was given of theexample in which the camera body 5A includes the imaging elementactuator 17 which drives the imaging element 12, but the restriction tothis configuration is unnecessary. The imaging element actuator 17 ofthe camera body 5A may be replaced with an electronic-type blurcorrection function which moves an area (cropping range) forphotographing an image on the image plane of the imaging element 12 inaccordance with the displacement amount. Moreover, the camera body 5Amay be configured to execute, in combination, the blur correction by theimaging element actuator 17 and the electronic-type blur correction.

Additionally, in the above-described second embodiment, theinterchangeable lens 4 is configured to include the angular velocitysensor 23, but the restriction to this is unnecessary. Theinterchangeable lens 4 in the second embodiment may be configured toacquire the displacement amount from the camera body 5A. According tothis configuration, the angular velocity sensor 23 in theinterchangeable lens 4 can be omitted.

Additionally, in the above-described second embodiment, such aconfiguration may be adopted that the correction in the interchangeablelens 4 and the correction by the camera body 5A are separately appliedwith respect to frequency components. For example, in the case of theconfiguration in which the correction in the interchangeable lens 4 iseffective for the blur occurring at a high frequency, and the correctionin the camera body 5A is effective for the blur occurring at a lowfrequency, the blur of the high frequency is corrected by theinterchangeable lens 4, and the blur of the low frequency is correctedby the camera body 5A. Thereby, a more appropriate blur correction canbe executed. Incidentally, how to allocate frequency components to thecorrection by the interchangeable lens 4 and to the correction by thecamera body 5A may be determined when the interchangeable lens 4 and thecamera body 5A are first connected, or, in other configuration, may bechanged by a judgement at each time.

Although the present invention was described based on the embodiments,the invention is not restricted to the above embodiments. Needless tosay, various modifications and applications may be made withoutdeparting from the spirit of the invention. In addition, in the abovedescriptions of the operational flowcharts, the operations are describedby using such words as “first” or “then” for convenience′ sake, but thisdoes not mean that it is indispensable to execute the operations in thedescribed order.

Furthermore, each of the processes by the above embodiments may bestored as a program which can be executed by a CPU or the like servingas a computer. Besides, the program may be stored in a storage medium ofan external storage device, such as a memory card, a magnetic disk, anoptical disc or a semiconductor memory, and may be distributed. Inaddition, the CPU or the like reads in the program stored in the storagemedium of the external storage device, and can execute theabove-described process by the operation of the CPU or the like beingcontrolled by the read-in program.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

The invention claimed is:
 1. A camera system comprising: aninterchangeable lens comprising: an image pickup optical systemconfigured to form an image on an image plane, a vibration reductionoptical system which is driven in a direction perpendicular to anoptical axis of the image pickup optical system, a blur amount detectionsensor configured to acquire a blur amount caused by a vibration of thecamera system, and a blur correction actuator configured to drive thevibration reduction optical system by a driving distance based on theblur amount, and a camera body on which the interchangeable lens ismounted comprising: an image sensor configured to acquire a photographof the image formed by the image pickup optical system, and a receptioncircuit configured to: acquire first lens information includingdistortion correction information for correcting distortion of the imagepickup optical system, calculate a displacement between the optical axisand an image center of the photograph of the image to determine a shapeof distortion of the image plane, and select a function indicating acorrelation between the shape of distortion on the image plane and thedriving distance of the vibration reduction optical system, and aprocesser configured to: calculate a converted displacement for thedisplacement based on the function, and execute distortion correction onthe photograph of the image based on the first lens information and theconverted displacement.
 2. The camera system of claim 1, wherein thereception circuit is further configured to: acquire, from theinterchangeable lens, second lens information including the drivingdistance of the vibration reduction optical system, and the processer isfurther configured to calculate the displacement, based on the drivingdistance acquired.
 3. The camera system of claim 2, wherein theinterchangeable lens further comprises a memory which stores the firstlens information, wherein the reception circuit is configured to acquirethe first lens information from the interchangeable lens.
 4. The camerasystem of claim 3, wherein the reception circuit is further configuredto acquire the first lens information from the interchangeable lens at atime of first communication after the camera body is connected to theinterchangeable lens, and to periodically acquire the second lensinformation from the interchangeable lens.
 5. The camera system of claim3, wherein the reception circuit is configured to acquire the first lensinformation from an external device via an information communicationnetwork, and to periodically acquire the second lens information fromthe interchangeable lens.
 6. The camera system of claim 2, wherein thereception circuit is configured to periodically acquire the second lensinformation from the interchangeable lens, while the photograph of theimage is being acquired by the image sensor.
 7. The camera system ofclaim 2, wherein the reception circuit is configured to periodicallyacquire the second lens information from the interchangeable lens, whenthe photograph of the image is acquired by the image sensor.
 8. Thecamera system of claim 1, wherein the function included in the firstlens information is a function of such a form that the converteddisplacement is calculated by multiplying the driving distance of thevibration reduction optical system by a coefficient which is a fixedconstant, and the processer is configured to calculate the converteddisplacement by multiplying the displacement between the optical axisand the image center of the photograph of the image by the coefficient.9. The camera system of claim 1, wherein the function included in thefirst lens information is an approximate expression which approximates ashape variation of distortion based on a decentering movement amount ofthe vibration reduction optical system by a shape variation ofdistortion based on the displacement between the optical axis and theimage center.
 10. The camera system of claim 2, wherein the image pickupoptical system includes a zooming optical system configured to vary afocal distance, and a focusing optical system configured to change afocus state of an image, the first lens information includes thefunction for each of combinations between a zoom position and a focusposition, the second lens information further includes a zoom positionand a focus position of the image pickup optical system, and theprocesser further selects the function, based on the zoom position andthe focus position.
 11. The camera system of claim 10, wherein thereception circuit is further configured to: acquire the first lensinformation from the interchangeable lens at a time of firstcommunication after the camera body is connected to the interchangeablelens, and to periodically acquire the second lens information from theinterchangeable lens, and the processer is configured to convert thedisplacement between the optical axis and the image center of thephotograph of the image by using the function, and to calculate theconverted displacement, each time the photograph of the image isacquired by the image sensor.
 12. The camera system of claim 1, whereinthe camera body further comprises an imaging element actuator configuredto drive the image sensor in a direction perpendicular to the opticalaxis by a driving amount corresponding to the blur amount, and theprocesser is configured to estimate the driving amount of the vibrationreduction optical system in accordance with a ratio in correction amountbetween the vibration reduction optical system and the imaging elementactuator, and a driving amount of the imaging element actuator.
 13. Thecamera system of claim 12, wherein the converted displacement is a sumbetween the driving amount of the imaging element actuator and a valuewhich is obtained by converting the estimated driving amount of thevibration reduction optical system by the function included in the firstlens information.
 14. The camera system of claim 13, wherein the imagepickup optical system includes a zooming optical system configured tovary a focal distance, and a focusing optical system configured tochange a focus state of an image, the first lens information includesthe function for each of combinations between a zoom position and afocus position, and the reception circuit is configured to acquiresecond lens information including a zoom position and a focus positionof the image pickup optical system from the interchangeable lens.
 15. Acamera body comprising: a lens mount on which an interchangeable lens ismounted; an image sensor configured to acquire a photograph of an imageformed in an image plane of an image pickup optical system of theinterchangeable lens, wherein the image pickup optical system has anoptical axis; a reception circuit configured to: acquire lensinformation including distortion correction information for correctingdistortion of the image pickup optical system, calculate a displacementbetween the optical axis and an image center of the photograph of theimage to determine a shape of distortion of the image plane, and selecta function indicating a correlation between a shape of distortion on theimage plane and a driving amount of a vibration reduction optical systemof the interchangeable lens, wherein the vibration reduction opticalsystem reduces an amount of blurring caused by vibration of the camerabody, and a processer communicatively coupled to the reception circuit,wherein the processer is configured to: calculate a converteddisplacement amount for the displacement based on the function, andexecute distortion correction on the photograph of the image, based onthe distortion correction information and the converted displacementamount.
 16. A control method of a camera system that has aninterchangeable lens and a camera body on which the interchangeable lensis mounted, wherein the interchangeable lens comprises an image pickupoptical system and a vibration reduction optical system, the controlmethod comprising: acquiring a blur amount caused by a vibration of thecamera system; driving, by a blur correction actuator, the vibrationreduction optical system a driving distance based on the blur amount,wherein the driving distance is in a direction perpendicular to anoptical axis of the camera system; acquiring, by an image sensor of thecamera body, a photograph of an image formed on an image plane of theimage pickup optical system; acquiring, by a processor of the camerabody, first lens information including distortion correction informationfor correcting distortion of the image pickup optical system;calculating, by the processor, a displacement between the optical axisand an image center of the photograph of the image to determine a shapeof distortion of the image plane; selecting a function indicating acorrelation between the shape of distortion on the image plane and thedriving distance of the vibration reduction optical system; calculatinga converted displacement for the displacement based on the function; andexecuting, by the processor, distortion correction on the photograph ofthe image, based on the distortion correction information and theconverted displacement.